/************************************************* md5 類實現了RSA Data Security, Inc.在提交給IETF 的RFC1321中的MD5 message-digest 算法。 *************************************************/public class MD5 {	/* 下面這些S11-S44實際上是一個4*4的矩陣，在原始的C實現中是用#define 實現的，	 這里把它們實現成為static final是表示了只讀，切能在同一個進程空間內的多個	 Instance間共享*/	static final int S11 = 7;	static final int S12 = 12;	static final int S13 = 17;	static final int S14 = 22;	static final int S21 = 5;	static final int S22 = 9;	static final int S23 = 14;	static final int S24 = 20;	static final int S31 = 4;	static final int S32 = 11;	static final int S33 = 16;	static final int S34 = 23;	static final int S41 = 6;	static final int S42 = 10;	static final int S43 = 15;	static final int S44 = 21;	static final byte[] PADDING = { -128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,			0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,			0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,			0, 0, 0, 0, 0, 0, 0 };	/* 下面的三個成員是MD5計算過程中用到的3個核心數據，在原始的C實現中	 被定義到MD5_CTX結構中	 	 */	private long[] state = new long[4]; // state (ABCD)	private long[] count = new long[2]; // number of bits, modulo 2^64 (lsb first)	private byte[] buffer = new byte[64]; // input buffer	/* digestHexStr是MD5的唯一一個公共成員，是最新一次計算結果的	 16進制ASCII表示.	 */	public String digestHexStr;	/* digest,是最新一次計算結果的2進制內部表示，表示128bit的MD5值.	 */	private byte[] digest = new byte[16];	/*	 getMD5ofStr是類MD5最主要的公共方法，入口參數是你想要進行MD5變換的字符串	 返回的是變換完的結果，這個結果是從公共成員digestHexStr取得的．	 */	public String getMD5ofStr(String inbuf) {		md5Init();		md5Update(inbuf.getBytes(), inbuf.length());		md5Final();		digestHexStr = "";		for (int i = 0; i < 16; i++) {			digestHexStr += byteHEX(digest[i]);		}		return digestHexStr;	}	// 這是MD5這個類的標準構造函數，JavaBean要求有一個public的并且沒有參數的構造函數	public MD5() {		md5Init();		return;	}	/* md5Init是一個初始化函數，初始化核心變量，裝入標準的幻數 */	private void md5Init() {		count[0] = 0L;		count[1] = 0L;		///* Load magic initialization constants.		state[0] = 0x67452301L;		state[1] = 0xefcdab89L;		state[2] = 0x98badcfeL;		state[3] = 0x10325476L;		return;	}	/* F, G, H ,I 是4個基本的MD5函數，在原始的MD5的C實現中，由于它們是	 簡單的位運算，可能出于效率的考慮把它們實現成了宏，在java中，我們把它們	 實現成了private方法，名字保持了原來C中的。 */	private long F(long x, long y, long z) {		return (x & y) | ((~x) & z);	}	private long G(long x, long y, long z) {		return (x & z) | (y & (~z));	}	private long H(long x, long y, long z) {		return x ^ y ^ z;	}	private long I(long x, long y, long z) {		return y ^ (x | (~z));	}	/* 	 FF,GG,HH和II將調用F,G,H,I進行近一步變換	 FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.	 Rotation is separate from addition to prevent recomputation.	 */	private long FF(long a, long b, long c, long d, long x, long s, long ac) {		a += F(b, c, d) + x + ac;		a = ((int) a << s) | ((int) a >>> (32 - s));		a += b;		return a;	}	private long GG(long a, long b, long c, long d, long x, long s, long ac) {		a += G(b, c, d) + x + ac;		a = ((int) a << s) | ((int) a >>> (32 - s));		a += b;		return a;	}	private long HH(long a, long b, long c, long d, long x, long s, long ac) {		a += H(b, c, d) + x + ac;		a = ((int) a << s) | ((int) a >>> (32 - s));		a += b;		return a;	}	private long II(long a, long b, long c, long d, long x, long s, long ac) {		a += I(b, c, d) + x + ac;		a = ((int) a << s) | ((int) a >>> (32 - s));		a += b;		return a;	}	/*	 md5Update是MD5的主計算過程，inbuf是要變換的字節串，inputlen是長度，這個	 函數由getMD5ofStr調用，調用之前需要調用md5init，因此把它設計成private的	 */	private void md5Update(byte[] inbuf, int inputLen) {		int i, index, partLen;		byte[] block = new byte[64];		index = (int) (count[0] >>> 3) & 0x3F;		// /* Update number of bits */		if ((count[0] += (inputLen << 3)) < (inputLen << 3))			count[1]++;		count[1] += (inputLen >>> 29);		partLen = 64 - index;		// Transform as many times as possible.		if (inputLen >= partLen) {			md5Memcpy(buffer, inbuf, index, 0, partLen);			md5Transform(buffer);			for (i = partLen; i + 63 < inputLen; i += 64) {				md5Memcpy(block, inbuf, 0, i, 64);				md5Transform(block);			}			index = 0;		} else			i = 0;		///* Buffer remaining input */		md5Memcpy(buffer, inbuf, index, i, inputLen - i);	}	/*	 md5Final整理和填寫輸出結果	 */	private void md5Final() {		byte[] bits = new byte[8];		int index, padLen;		///* Save number of bits */		Encode(bits, count, 8);		///* Pad out to 56 mod 64.		index = (int) (count[0] >>> 3) & 0x3f;		padLen = (index < 56) ? (56 - index) : (120 - index);		md5Update(PADDING, padLen);		///* Append length (before padding) */		md5Update(bits, 8);		///* Store state in digest */		Encode(digest, state, 16);	}	/* md5Memcpy是一個內部使用的byte數組的塊拷貝函數，從input的inpos開始把len長度的	 字節拷貝到output的outpos位置開始 	 */	private void md5Memcpy(byte[] output, byte[] input, int outpos, int inpos,			int len) {		int i;		for (i = 0; i < len; i++)			output[outpos + i] = input[inpos + i];	}	/*	 md5Transform是MD5核心變換程序，有md5Update調用，block是分塊的原始字節	 */	private void md5Transform(byte block[]) {		long a = state[0], b = state[1], c = state[2], d = state[3];		long[] x = new long[16];		Decode(x, block, 64);		/* Round 1 */		a = FF(a, b, c, d, x[0], S11, 0xd76aa478L); /* 1 */		d = FF(d, a, b, c, x[1], S12, 0xe8c7b756L); /* 2 */		c = FF(c, d, a, b, x[2], S13, 0x242070dbL); /* 3 */		b = FF(b, c, d, a, x[3], S14, 0xc1bdceeeL); /* 4 */		a = FF(a, b, c, d, x[4], S11, 0xf57c0fafL); /* 5 */		d = FF(d, a, b, c, x[5], S12, 0x4787c62aL); /* 6 */		c = FF(c, d, a, b, x[6], S13, 0xa8304613L); /* 7 */		b = FF(b, c, d, a, x[7], S14, 0xfd469501L); /* 8 */		a = FF(a, b, c, d, x[8], S11, 0x698098d8L); /* 9 */		d = FF(d, a, b, c, x[9], S12, 0x8b44f7afL); /* 10 */		c = FF(c, d, a, b, x[10], S13, 0xffff5bb1L); /* 11 */		b = FF(b, c, d, a, x[11], S14, 0x895cd7beL); /* 12 */		a = FF(a, b, c, d, x[12], S11, 0x6b901122L); /* 13 */		d = FF(d, a, b, c, x[13], S12, 0xfd987193L); /* 14 */		c = FF(c, d, a, b, x[14], S13, 0xa679438eL); /* 15 */		b = FF(b, c, d, a, x[15], S14, 0x49b40821L); /* 16 */		/* Round 2 */		a = GG(a, b, c, d, x[1], S21, 0xf61e2562L); /* 17 */		d = GG(d, a, b, c, x[6], S22, 0xc040b340L); /* 18 */		c = GG(c, d, a, b, x[11], S23, 0x265e5a51L); /* 19 */		b = GG(b, c, d, a, x[0], S24, 0xe9b6c7aaL); /* 20 */		a = GG(a, b, c, d, x[5], S21, 0xd62f105dL); /* 21 */		d = GG(d, a, b, c, x[10], S22, 0x2441453L); /* 22 */		c = GG(c, d, a, b, x[15], S23, 0xd8a1e681L); /* 23 */		b = GG(b, c, d, a, x[4], S24, 0xe7d3fbc8L); /* 24 */		a = GG(a, b, c, d, x[9], S21, 0x21e1cde6L); /* 25 */		d = GG(d, a, b, c, x[14], S22, 0xc33707d6L); /* 26 */		c = GG(c, d, a, b, x[3], S23, 0xf4d50d87L); /* 27 */		b = GG(b, c, d, a, x[8], S24, 0x455a14edL); /* 28 */		a = GG(a, b, c, d, x[13], S21, 0xa9e3e905L); /* 29 */		d = GG(d, a, b, c, x[2], S22, 0xfcefa3f8L); /* 30 */		c = GG(c, d, a, b, x[7], S23, 0x676f02d9L); /* 31 */		b = GG(b, c, d, a, x[12], S24, 0x8d2a4c8aL); /* 32 */		/* Round 3 */		a = HH(a, b, c, d, x[5], S31, 0xfffa3942L); /* 33 */		d = HH(d, a, b, c, x[8], S32, 0x8771f681L); /* 34 */		c = HH(c, d, a, b, x[11], S33, 0x6d9d6122L); /* 35 */		b = HH(b, c, d, a, x[14], S34, 0xfde5380cL); /* 36 */		a = HH(a, b, c, d, x[1], S31, 0xa4beea44L); /* 37 */		d = HH(d, a, b, c, x[4], S32, 0x4bdecfa9L); /* 38 */		c = HH(c, d, a, b, x[7], S33, 0xf6bb4b60L); /* 39 */		b = HH(b, c, d, a, x[10], S34, 0xbebfbc70L); /* 40 */		a = HH(a, b, c, d, x[13], S31, 0x289b7ec6L); /* 41 */		d = HH(d, a, b, c, x[0], S32, 0xeaa127faL); /* 42 */		c = HH(c, d, a, b, x[3], S33, 0xd4ef3085L); /* 43 */		b = HH(b, c, d, a, x[6], S34, 0x4881d05L); /* 44 */		a = HH(a, b, c, d, x[9], S31, 0xd9d4d039L); /* 45 */		d = HH(d, a, b, c, x[12], S32, 0xe6db99e5L); /* 46 */		c = HH(c, d, a, b, x[15], S33, 0x1fa27cf8L); /* 47 */		b = HH(b, c, d, a, x[2], S34, 0xc4ac5665L); /* 48 */		/* Round 4 */		a = II(a, b, c, d, x[0], S41, 0xf4292244L); /* 49 */		d = II(d, a, b, c, x[7], S42, 0x432aff97L); /* 50 */		c = II(c, d, a, b, x[14], S43, 0xab9423a7L); /* 51 */		b = II(b, c, d, a, x[5], S44, 0xfc93a039L); /* 52 */		a = II(a, b, c, d, x[12], S41, 0x655b59c3L); /* 53 */		d = II(d, a, b, c, x[3], S42, 0x8f0ccc92L); /* 54 */		c = II(c, d, a, b, x[10], S43, 0xffeff47dL); /* 55 */		b = II(b, c, d, a, x[1], S44, 0x85845dd1L); /* 56 */		a = II(a, b, c, d, x[8], S41, 0x6fa87e4fL); /* 57 */		d = II(d, a, b, c, x[15], S42, 0xfe2ce6e0L); /* 58 */		c = II(c, d, a, b, x[6], S43, 0xa3014314L); /* 59 */		b = II(b, c, d, a, x[13], S44, 0x4e0811a1L); /* 60 */		a = II(a, b, c, d, x[4], S41, 0xf7537e82L); /* 61 */		d = II(d, a, b, c, x[11], S42, 0xbd3af235L); /* 62 */		c = II(c, d, a, b, x[2], S43, 0x2ad7d2bbL); /* 63 */		b = II(b, c, d, a, x[9], S44, 0xeb86d391L); /* 64 */		state[0] += a;		state[1] += b;		state[2] += c;		state[3] += d;	}	/*Encode把long數組按順序拆成byte數組，因為java的long類型是64bit的，	 只拆低32bit，以適應原始C實現的用途	 */	private void Encode(byte[] output, long[] input, int len) {		int i, j;		for (i = 0, j = 0; j < len; i++, j += 4) {			output[j] = (byte) (input[i] & 0xffL);			output[j + 1] = (byte) ((input[i] >>> 8) & 0xffL);			output[j + 2] = (byte) ((input[i] >>> 16) & 0xffL);			output[j + 3] = (byte) ((input[i] >>> 24) & 0xffL);		}	}	/*Decode把byte數組按順序合成成long數組，因為java的long類型是64bit的，	 只合成低32bit，高32bit清零，以適應原始C實現的用途	 */	private void Decode(long[] output, byte[] input, int len) {		int i, j;		for (i = 0, j = 0; j < len; i++, j += 4)			output[i] = b2iu(input[j]) | (b2iu(input[j + 1]) << 8)					| (b2iu(input[j + 2]) << 16) | (b2iu(input[j + 3]) << 24);		return;	}	/*	 b2iu是我寫的一個把byte按照不考慮正負號的原則的＂升位＂程序，因為java沒有unsigned運算	 */	public static long b2iu(byte b) {		return b < 0 ? b & 0x7F + 128 : b;	}	/*byteHEX()，用來把一個byte類型的數轉換成十六進制的ASCII表示，	 因為java中的byte的toString無法實現這一點，我們又沒有C語言中的	 sprintf(outbuf,"%02X",ib)	 */	public static String byteHEX(byte ib) {		char[] Digit = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A',				'B', 'C', 'D', 'E', 'F' };		char[] ob = new char[2];		ob[0] = Digit[(ib >>> 4) & 0X0F];		ob[1] = Digit[ib & 0X0F];		String s = new String(ob);		return s;	}	public static void main(String args[]) {		MD5 m = new MD5();		System.out.println("MD5(\"abc\"):" + m.getMD5ofStr("abc"));	}}